I don’t agree with the parent that the solution for SEO spam is paying for the search engine (I think there are other good reasons to do this though), especially since people have been doing things like naming their company “AAA Auto Repair” to be first in the phone book since before computers ever existed. But the person you originally replied to does have a point in blaming Google for the problem. Most SEO spam sites make their money from ads, and Google are the ones who run the ad network, which means Google are the ones funding them and creating an incentive for them to exist.

> SEO is the practice done by webmasters of optimizing a website to improve its visibility and ranking in search engine results.

They do this because they benefit from their site being visited or the information they are providing being noticed.

> If you are paying to use your search engine, does that mean webmasters are no longer incentivized to/will not try to improve their visibility/ranking in your search results?

I see no reason it would have that effect. It does, however, create different incentives for the search provider to improve the signals indicating page relevance since the user is the priority instead of advertisers.